As New Zealand begins the long recovery from this week's deadly earthquake, video journalist David Brill has been getting the personal stories from what's been described as the country's 'darkest day'.

David's on the streets of Christchurch, as the search for survivors continues and residents struggle with shortages of basic supplies.

He also heads out to the small community of Lyttelton; close to the epicentre and severely damaged, with aftershocks interrupting its recovery and David's filming.

A magnitude 6.3 earthquake will occur when an active fault area approximately 15km square ruptures, and one side moves about one metre relative to the other.

Its effect depends on how close it is to a population centre, and ground shaking will be severe within 10 to 20 kilometres of the rupture.

The critical issue with this earthquake was that the epicentre was at shallow depth (5km) under Christchurch, so many people were within 10km to 20km of the fault rupture.

The magnitude 7.1 earthquake on September 4 last year was 30km to 40km west of Christchurch and ruptured mainly to the west.

Q: Should we expect further large earthquakes in the area? Are aftershocks likely?

The September earthquake and this earthquake will have relieved the majority of stress in the regions in which they occurred, so another larger earthquake is unlikely.

However, aftershocks will certainly occur over the next few days and weeks which may cause further damage in weakened buildings, and will be very distressing for residents.

Q: Is there a geological reason for multiple large earthquakes occurring within such a short time?

Earthquakes always cluster in time and space with some large earthquakes having foreshocks and most large earthquakes have many aftershocks.

Multiple large earthquakes are not uncommon, often when the main rupture of the earlier event is extended into an adjacent segment of the active fault.

Q: Why is the New Zealand South Island so geologically active?

New Zealand is on the tectonic plate boundary between the Pacific Plate and the Australia-India Plate.

The plate boundary is east of the North Island and crosses to the west of South Island.

Christchurch is not on the plate boundary, but is near to related secondary faults that result from the bend in the plate boundary to the north.

In the past 200 years, and in the long term, large earthquakes will occur less frequently in Christchurch than along the plate boundary.

However all earthquakes in the Christchurch region will be shallow, so the effect of a given earthquake will be worse than from a deeper plate boundary earthquake of the same magnitude.

Q: How does this rate historically against other earthquakes?

This is by far the largest earthquake to have occurred in the Christchurch region in historic time.

Earthquakes larger than magnitude 6.0, usually deeper than this event, occur about annually in New Zealand, including one of magnitude 7.8 that occurred in the remote southwest of South Island in July 2009 with little damage.

Q: Why is New Zealand seemingly more prone to earthquakes than Australia? Is a similar earthquake likely to occur in Australia?

New Zealand is more prone to earthquakes because it is on the plate boundary and has many plate boundary earthquakes. Large earthquakes occur infrequently in Australia.

In all of Australia, a magnitude 6.0 or larger event occurs on average every 10 years.

In the capital cities of Australia, a nearby magnitude 6.0 will occur on average every few thousand years. All earthquakes in Australia are at shallow depth, similar to those in Christchurch.

Q: Is it possible to predict earthquake activity? How much better are we at predicting them and how good can we hope to get?

It is not possible to predict earthquakes, giving location, time of occurrence and magnitude, with certainty.

Aftershocks have continued at a decreasing rate since the September earthquake. Recent aftershocks have been east of the original rupture.

Q: Are there engineering or town planning measures which could be improved to reduce the impact of earthquakes?

Building standards are already very high in New Zealand, but are upgraded as knowledge develops, and as higher standards become economically viable.

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Transcript

In all the media coverage of this week's devastating earthquake, it was New Zealand Prime Minister John Key who perhaps best summed up the disaster, he said simply we may well be witnessing New Zealand's darkest day. As the death toll rose throughout the week it was hard to disagree with those words. When news of the tragedy broke on Tuesday we sent our veteran correspondent David Brill to Christchurch. For decades David has covered wars and natural disasters all over the world.

REPORTER: David Brill

YALDA HAKIM: Welcome back, David.

DAVID BRILL, VIDEO JOURNALIST: Thanks Yalda.

YALDA HAKIM: David, you arrived soon after the earth quake. What were your first impressions?

DAVID BRILL: When I got there into the city or the city - area it was all cordoned off - it was very hard to move around. They had tanks out, they had police and they had the military out to stop the people from going into the city. But you could just see on the faces, some of the people wandering around - of how desperate they were and how lonely they looked, they didn't know what to do there was no help for them, they were finding it hard to get milk or they couldn't drink the water - the electricity was out.

WOMAN: It was a two storey house and it has collapsed now to one single storey and it's gone on to the drive and it must have slid about 3m.

REPORTER: There was a lady in there, was there?

WOMAN: There was.

Petrol is another hard thing to get there - they were rationing petrol to $30 for each car. The cars were lined up for blocks waiting to see if they could get petrol.

REPORTER: You don't have any what?

SERVICE STATION ATTENDANT: No petrol coming in.

REPORTER: No petrol coming in?

SERVICE STATION ATTENDANT: Not at this stage.

It's very devastating because there is not much you can do yourself to help. It's quite frightening and then the after shocks - I think the time I was there, there were 250 after shocks. That's so bad for young children to know that something is going to happen, not really knowing what it is and not knowing when it is going to happen.

LITTLE GIRL: Well you needed to go to the back field and wait for our parents to come.

REPORTER: Was it very scary?

LITTLE GIRL: No not for me. But my friend cried...

YALDA HAKIM: Must have also been eerie while you were filming in Christchurch to know that there were still many, many people still trapped under the buildings.

DAVID BRILL: The police put on a bus for some of the media to go right into the heart of the city, the CBD. They didn't want to take people in there. There was nobody in there except for worker who is were trying to get people out alive or dead. It was again a very eerie experience and we went to the famous cathedral which was very severely damaged. And still now there are 20 people believed dead in there, they can't get out and looking at that, it's a very powerful strange feeling.

REPORTER: How is it all going?

MURRAY TRAYNOR, NSW AMBULANCE SERVICE: It's a slow process.

REPORTER: When did you come over?

MURRAY TRAYNOR: Yesterday morning.

REPORTER: How long are you staying for?

MURRAY TRAYNOR: We are here for 10 days.

REPORTER: When you say slow progress, just tell me what you are looking for?

MURRAY TRAYNOR: We're looking for any surviving life that is in the building.

REPORTER: Have you found any yet?

MURRAY TRAYNOR: Not so far today.

DAVID BRILL: Around the streets actually in the CBD area most of the businesses have all collapsed or broken down or the glass has all smashed in some of these shops. That's what they are worried about, looters going in - which they were. They see anybody in the city who is not meant to be there they will arrest them immediately. But to see these shops, tourist shops, the New Zealand T-shirt and various things for tourists just all broken and I can't see it ever for a long, long time ever getting back on its feet.

YALDA HAKIM: Of course you weren't just in Christchurch, you ventured out to other areas, what did you find?

DAVID BRILL: I heard about this town of Lyttelton about 20 minutes away from Christchurch, a beautiful coastal town which is the shipping point port for Christchurch. We could not go through the tunnels so we went over the mountains and looking down on this beautiful town on this port, there were craters in the road and boulders and I was worried about after shocks happening while we were driving in because the boulders could move and squash the car. But we got in all right and it was just so quiet. You could look into the town itself, the churches - two wonderful old churches were totally destroyed. Shops, famous old hotels, totally destroyed.

YALDA HAKIM: You met a man called John Sellwood in Lyttelton, what happened to him?

DAVID BRILL: Well John Sellwood's house - it was a wooden house which a lot of these houses are. It was on a cliff area overlooking this beautiful bay in Lyttelton and he said, "Would you like to come inside and have a look"

JOHN SELLWOOD, RESIDENT, LYTTELTON: We weren't here and we were damned lucky, because this was the bedroom. Be careful, because that chimney is about to go so rush through here, rush through there. There is going to be weeks of going through rubble.

DAVID BRILL:Fridges turned upside down, bookcases gone everywhere, furniture - the fireplace falling down, the ceiling falling down. I was interviewing him talking to him about it and he was telling me that he hoped to get the home back together at some time;... And an after shock came so we had to make a run for it into another room.

YALDA HAKIM: It really does seem from the stories we're hearing that the people of New Zealand have bonded through this catastrophe.

DAVID BRILL: Very much so, it brings out the best in people - I have noticed that before in disasters. Working together, for instance - the lack of water, I walked past one place and somebody put out 20 bottles of fresh water saying please help yourself to this free boiled water. Little things like that.

ANDREW TURNER, SHOPKEEPER, LYTTELTON: People just working together to make sure people have the resources and help and support that they need. I'm really impressed at the way the community has come together here to just really look after each other and look after people that have needs at the moment.

JOHN SELLWOOD: Towns are made of the people. They are made of people. The bricks and mortar...

REPORTER: Gee, there we go again. That was a bad one - there is glass popping out over there.

JOHN SELLWOOD: This is constant - this is constant so people's nerves are constantly jangled.

REPORTER: That's right. How long does it take to get over that - that was a bad one or was it normal?

JOHN SELLWOOD: That was normal.

REPORTER: There have probably been nearly 200 after shocks.

JOHN SELLWOOD: It's living on shaky ground isn't it, living on shaky ground. You had a sense of terra firma - of your life being solid, everything of your life being predictable. Suddenly nothing is predictable anymore and so the future is not necessarily long term, but day by day. It's just working those things. I don't necessarily think that's a bad thing - it's just the way it is. You have to say that this is what it is. There is no point in saying, "Can I change this." You can't. This is what it is, just deal with it. This is what we will have to do - that is what you are gonna have to do.

ANDREW TURNER: Yesterday lunchtime before we started trading everything here was just a sea of products all over the floor. All of these shelves and counters and refrigeration and everything had moved - I was actually in here when the big earthquake happened on Tuesday. I stood at the end of the counter here and I held onto the ice cream counter as hard as I could. It was absolutely terrifying and as soon as the big shaking was over I was out the door and picking my way through a sea of stock that was on the floor. All of these fridges had jumped forward by half a metre. Everything was everywhere.

DAVID BRILL: When I came down on the plane from Wellington to Christchurch most people on that plane were trying to get down to see if their relatives were alive. They had no communication - people weren't answering on mobiles or they couldn't get through. So they were just devastated not being able to get in contact with their loved ones and it's still going on.

YALDA HAKIM: When do you think the people of Christchurch will recover from this?

DAVID BRILL: Years. It will take years Yalda. The city is I think finished until they start rebuilding, which will take a long time. One of the fire chiefs said to me that a lot of the buildings that are still standing are not safe, they will have to take them down as they go along and rebuild Christchurch.

MIKE HALL, NEW ZEALAND FIRE CHIEF: When you look at the old buildings, really, the heritage heart of Christchurch has been pretty much destroyed ...

REPORTER: It's a beautiful city.

MIKE HALL: It's a lovely city - a colonial city, it'd been destroyed by the September earthquake and now this one on top of it. A lot of buildings they hope to save, they simply won't be able to so I think we will see a lot of the old buildings pulled down and replaced with modern architecture and that will change the heart of Christchurch and change the feel of the city I think.

DAVID BRILL: You know Christchurch was a city for tourists - well tourists won't go there and so there will be no work for a lot of people who have got these shops - tourist shops and so forth. It will take many years and it will never be the same again. But what I noticed, the New Zealanders are very resilient people, very tough, terrific and I asked the question to many of them "œIs it time for you to go, do you think? You have had two earthquakes in under six months. Will you stay here?" They said "œYes we will rebuild and get the city back again." Well that's at the moment and I think it will be a lot worse as the months and weeks go on, though.

YALDA HAKIM: Our thoughts and prayers are with the people of New Zealand tonight. So why was this quake much more devastating than previous ones in New Zealand. You can go to our website for information from experts on this quake and others, plus a photo gallery with pictures from local residents and also links to SBS news coverage.